Before the first century CE, there were some small differences between copies of the Hebrew Bible. During first century CE, Jewish Bible specialists agreed on the same words, a process called standardisation.

Between about 100 and 300 CE, a group of Jewish Bible specialists called the Tannaim copied this Hebrew Bible. Then between about 300 and 500 CE, another group of Jewish Bible specialists called the Amoraim continued the work of the Tannaim. The Masoretes then continued the Amoraim's work for the next 500 years.

The Masoretes were very careful when they copied the Bible. When they thought there was a mistake in the work of the Amoraim or the other specialists, they wrote a note in the side of the book, rather than change the book. After they copied a book, they counted the verses, words and letters in each book to make sure there were no mistakes.

The Masoretes also added vowel points to make the Bible easier to read because the Hebrew writing does not show vowels.

There were two main places where Masoretes worked: Babylon and Israel. The Masoretes also wrote book about the Bible called the Masorah.